This study suggests that low levels of serum Mg may be an important predictor of SCD, and warrants further research into the effectiveness of Mg supplementation for those considered to be at high risk for SCD. Sudden cardiac death (SCD) is a major public health problem comprising more than half of all cardiovascular disease (CVD) deaths in the USA. 1 Even with estimates of coronary heart disease (CHD) mortality declining by more than 50% from 1950 to 1999, the relative proportion of SCD of all CVD deaths in the USA simultaneously increased during this time. Secular trends in Olmsted County, Minnesota from 1979 to 2003 have shown much larger declines in in-hospital death rates, with declines in out-of-hospital death rates occurring much more slowly. Major risk factors for SCD include hypertension, diabetes, smoking, family history of myocardial infarction, and obesity, but the majority of SCDs occur in those with no prior history of CVD.
Magnesium (Mg), a micronutrient and common cation in the human body, is a natural calcium antagonist and modulates vasomotor tone, blood pressure, and peripheral blood flow. Though virtually all Mg is stored in cells, low levels of serum Mg are usually predictive of low levels of total body Mg as well. Previous epidemiological studies have reported that serum and dietary Mg are associated inversely with CVD risk factors such as hypertension, type 2 diabetes mellitus, the metabolic syndrome, in addition to CHD. Additional evidence from ecologic, clinical, and autopsy studies has shown higher Mg to be potentially protective against SCD, but no prospective studies have reported the association of Mg levels with incidence of SCD in the general population. In addition to its role in the regulation of blood pressure and maintenance of vascular smooth muscle tone, Mg deficiencies are known to cause ventricular arrhythmias, the most common precursors to SCD. Serum Mg levels are modified by intake of dietary Mg, calcium (Ca) and potassium (K), in addition to alcohol intake and physical exercise.